Arguments are made for a few different kings deemed to control enough of the ancient kingdoms of the Anglo-Saxons to be deemed the first King of England. For example Offa, king of Mercia, and Egbert, king of Wessex, are sometimes described as kings of England by popular writers, but not by all historians. In the late eighth century Offa achieved a dominance over southern England which did not survive his death in 796. In 829 Egbert conquered Mercia, but he soon lost control of it. By the late ninth century Wessex was the dominant Anglo-Saxon kingdom. Its king, Alfred the Great, was overlord of western Mercia and used the title King of the Angles and Saxons, but he never ruled eastern and northern England, which was then the Danelaw. His son Edward the Elder conquered the eastern Danelaw, but Edward's son Æthelstan became the first king to rule the whole of England when he conquered Northumbria in 927, and he is regarded by some modern historians as the first king of England.[1][2]

There is some evidence that Ælfweard of Wessex may have been king for four weeks in 924, between his father Edward the Elder and his brother Æthelstan, although he was not crowned.[6] However, this is not accepted by all historians. Also, it is unclear whether Ælfweard was declared king of the whole kingdom or of Wessex only: there is evidence that when Edward died, Ælfweard was declared king in Wessex and Æthelstan in Mercia.[7]

Following the death of Sweyn Forkbeard, Æthelred the Unready returned from exile and was again proclaimed king on 3 February 1014. His son succeeded him after being chosen king by the citizens of London and a part of the Witan,[25] despite ongoing Danish efforts in wresting the crown from the West Saxons.

Following the decisive Battle of Assandun on 18 October 1016, King Edmund signed a treaty with Cnut in which all of England except for Wessex would be controlled by Cnut.[27] Upon Edmund's death on 30 November, Cnut ruled the whole kingdom as its sole king.

Empress Matilda was declared heir presumptive by her father, Henry I, after the death of her brother on the White Ship, and acknowledged as such by the barons. However, upon Henry I's death, the throne was seized by Matilda's cousin, Stephen of Blois. The Anarchy ensued, with Matilda being a de facto ruler for a few months in 1141—the first woman so to be—but she was never crowned and is rarely listed as a monarch of England.[35]

Count Eustace IV of Boulogne (c. 1130 – 17 August 1153) was appointed co-king of England by his father, King Stephen, on 6 April 1152, in order to guarantee his succession to the throne (as was the custom in France, but not in England). However, the Pope and the Church would not agree to this, and Eustace was not crowned. Eustace died the next year aged 22, during his father's lifetime, and so never became king in his own right.[37]

Stephen came to an agreement with Matilda in November 1153 with the signing of the Treaty of Wallingford, where Stephen recognised Henry, son of Matilda, as the heir-apparent to the throne in lieu of his own son, who had died that August.

The Angevins ruled over the Angevin Empire during the 12th and 13th centuries, an area stretching from the Pyrenees to Ireland. They did not regard England as their primary home until most of their continental domains were lost by John. Though the Angevin Dynasty was short-lived, their male line descendants included the House of Plantagenet, the House of Lancaster and the House of York.

Louis VIII of France briefly ruled about half of England from 1216 to 1217 at the conclusion of the First Barons' War against King John. On marching into London he was openly received by the rebel barons and citizens of London and proclaimed (though not crowned) king at St Paul's cathedral. Many nobles, including Alexander II of Scotland for his English possessions, gathered to give homage to him. However, in signing the Treaty of Lambeth in 1217, Louis conceded that he had never been the legitimate king of England.

The House of Plantagenet effectively started under Henry II of England, though today historians generally refer to Henry II and his sons as the Angevins due to their vast continental Empire. Historians instead begin the Plantagenet line from Henry III when the Plantagenet kings became more English in nature. The Houses of Lancaster and York are cadet branches of the House of Plantagenet.

This house descended from Edward III's third surviving son, John of Gaunt. Henry IV seized power from Richard II (and also displaced the next in line to the throne, Edmund Mortimer, a descendant of Edward III's second son, Lionel of Antwerp).

The House of York inherited its name from the fourth surviving son of Edward III, Edmund, 1st Duke of York, but claimed the right to the throne through Edward III's second surviving son, Lionel of Antwerp.

The Wars of the Roses (1455–1485) saw the throne pass back and forth between the rival houses of Lancaster and York.

The Tudors descended matrilineally from John Beaufort, one of the illegitimate children of John of Gaunt (third surviving son of Edward III), by Gaunt's long-term mistress Katherine Swynford. Those descended from English monarchs only through an illegitimate child would normally have no claim on the throne, but the situation was complicated when Gaunt and Swynford eventually married in 1396 (25 years after John Beaufort's birth). In view of the marriage, the church retroactively declared the Beauforts legitimate via a papal bull the same year (also enshrined in an Act of Parliament in 1397). A subsequent proclamation by John of Gaunt's legitimate son, King Henry IV, also recognised the Beauforts' legitimacy, but declared them ineligible ever to inherit the throne. Nevertheless, the Beauforts remained closely allied with Gaunt's other descendants, the Royal House of Lancaster.

John Beaufort's granddaughter Lady Margaret Beaufort was married to Edmund Tudor. Tudor was the son of Welsh courtier Owain Tewdwr or Tudur (anglicised to Owen Tudor) and Catherine of Valois, the widowed queen consort of the Lancastrian King Henry V. Edmund Tudor and his siblings were either illegitimate, or the product of a secret marriage, and owed their fortunes to the goodwill of their legitimate half-brother King Henry VI. When the House of Lancaster fell from power, the Tudors followed. By the late 15th century, the Tudors were the last hope for the Lancaster supporters. Edmund Tudor's son became king as Henry VII after defeating Richard III at the Battle of Bosworth Field in 1485, ending the Wars of the Roses.

Edward VI named Lady Jane Grey as his heir presumptive, overruling the order of succession laid down by Parliament in the Third Succession Act. Four days after his death on 6 July 1553, Jane was proclaimed queen—the first of three Tudor women to be proclaimed queen regnant. Nine days after the proclamation, on 19 July, the Privy Council switched allegiance and proclaimed Edward VI's Catholic half-sister Mary. Jane was executed in 1554, aged 16. Many historians do not consider her to have been a legitimate monarch.

Under the terms of the marriage treaty between Philip I of Naples (Philip II of Spain from 15 January 1556) and Queen Mary I, Philip was to enjoy Mary's titles and honours for as long as their marriage should last. All official documents, including Acts of Parliament, were to be dated with both their names, and Parliament was to be called under the joint authority of the couple. An Act of Parliament gave him the title of king and stated that he "shall aid her Highness ... in the happy administration of her Grace's realms and dominions"[47] (although elsewhere the Act stated that Mary was to be "sole queen"). Nonetheless, Philip was to co-reign with his wife.[48] As the new King of England could not read English, it was ordered that a note of all matters of state should be made in Latin or Spanish.[48][49][50] Coins were minted showing the heads of both Mary and Philip, and the coat of arms of England (right) was impaled with Philip's to denote their joint reign.[51][52] Acts which made it high treason to deny Philip's royal authority were passed in England[53] and Ireland.[54] In 1555, Pope Paul IV issued a papal bull recognising Philip and Mary as rightful King and Queen of Ireland.

Following the death of Elizabeth I in 1603 without issue, her cousin, James VI, King of Scots, succeeded to the English throne as James I in the Union of the Crowns. James was descended from the Tudors through his great-grandmother, Margaret Tudor, the eldest daughter of Henry VII. In 1604, he adopted the title King of Great Britain. However, the two parliaments remained separate until the Acts of Union 1707.[55]

Although the monarchy was restored in 1660, no stable settlement proved possible until the Glorious Revolution of 1688, when Parliament passed legislation prohibiting Roman Catholics from succeeding to the throne.[citation needed]

England, Scotland, and Ireland had shared a monarch for more than a hundred years, since the Union of the Crowns in 1603, when King James VI of Scotland inherited the English and Irish thrones from his first cousin twice removed, Queen Elizabeth I. Although described as a Union of Crowns, until 1707 there were in fact two separate Crowns resting on the same head. There had been attempts in 1606, 1667, and 1689, to unite England and Scotland by Acts of Parliament, but it was not until the early eighteenth century that the idea had the support of both political establishments behind it, albeit for rather different reasons.

Edmund the Magnificent: Rex Britanniæ ("King of Britain") and Rex Anglorum cæterarumque gentium gobernator et rector ("King of the English and of other peoples' and director")

Eadred: Regis qui regimina regnorum Angulsaxna, Norþhymbra, Paganorum, Brettonumque ("Reigning over the governments of the kingdoms of the Anglo-Saxons, Northumbrians, Pagans, and British")

Eadwig the Fair: Rex nutu Dei Angulsæxna et Northanhumbrorum imperator paganorum gubernator Breotonumque propugnator ("King by the will of God, Emperor of the Anglo-Saxons and Northumbrians, governor of the pagans, commander of the British")

Edgar the Peaceful: Totius Albionis finitimorumque regum basileus ("Autocrat of all Albion and its neighbouring realms")

Canute: Rex Anglorum totiusque Brittannice orbis gubernator et rector ("King of the English and of all the British sphere governor and director") and Brytannie totius Anglorum monarchus ("Monarch of all the English of Britain")

In the Norman periodRex Anglorum remained standard, with occasional use of Rex Anglie ("King of England"). The Empress Matilda styled herself Domina Anglorum ("Lady of the English").

From the time of King John onwards all other titles were eschewed in favour of Rex or Regina Anglie.

In 1604 James I, who had inherited the English throne the previous year, adopted the title (now usually rendered in English rather than Latin) King of Great Britain. The English and Scottish parliaments, however, did not recognise this title until the Acts of Union of 1707 under Queen Anne (who was of course Queen of Great Britain rather than king).[65]

^ abAfter reigning for approximately 9 weeks, Edgar the Atheling submitted to William the Conqueror, who had gained control of the area to the south and immediate west of London ("Eadgar (the Ætheling) - Archontology.org". Retrieved 26 October 2007.).

^Matilda is not listed as a monarch of England in many genealogies within texts, including David Carpenter's A Struggle for Mastery (2003) pg. 533, W.L. Warren's Henry II (1973) pg. 176, and John Gillingham's The Angevin Empire (1984) pg. x.

^The date of Edward II's death is disputed by Ian Mortimer in his book "The Perfect King: The Life of Edward III, Father of the English Nation," which argues that he may not have been murdered, but held imprisoned in Europe for several more years: ISBN 0-09-952709-X

^Philip was not meant to be a mere consort; rather, the status of Mary I's husband was envisioned as that of a co-monarch during her reign. See Act for the Marriage of Queen Mary to Philip of Spain. However the extent of his authority and his status are ambiguous. The Act says that Philip shall have the title of king and "shall aid her Highness ... in the happy administration of her Grace's realms and dominions," but elsewhere says that Mary shall be the sole Queen.